1. Field of the Invention
The invention in general relates to diagnostic apparatus, and particularly to a sensor-based system for on-line realtime monitoring.
2. Description of the Prior Art
Complex industrial or other operating systems generally have a plurality of sensors for monitoring various parameters during operation, not only for control purposes but for purposes of monitoring the system to detect actual or impending malfunctions.
Some systems may utilize dozens, if not hundreds, of sensors in the diagnostic process and very often the sensors may fail, degrade, or provide spurious readings not related to the actual parameter being measured.
Use of erroneous sensor data in the diagnostic process can lead to erroneous conclusions about possible malfunctions. In one respect, a malfunction may be indicated where, in fact, no malfunction exists and conversely a malfunction may be occurring or may occur without its detection and without proper notification to the system operator. Such event can represent a tremendous economic loss as well as a potentially dangerous situation.
To obviate these potential problems, some systems utilize redundant sensors such that if one fails another may take its place. For systems utilizing hundreds of sensors, such solution may be unfeasible, from an economic standpoint. In other types of systems, sensor readings are preprocessed prior to the system diagnosis and eliminated from consideration if their readings exceed certain boundaries. With such an arrangement, however, valuable information relative to the sensor degradation history which may be utilized in the diagnostic process, is lost.
The present invention provides for a diagnostic system which can recognize operating problems while they may be little more than a vague trend, and may do so taking into account sensor degradation or failure.